Qualitative changes of total cytoplasmic RNA size patterns in estrogen-induced adenoma in female rats

Estradiol was administered 2.5 mg once a week for 4, 8 and 16 weeks to female Wistar rats. Hyperprolactinemia corresponding to the size of the pituitary developed along the pituitary enlargement after 4 weeks and macroscopically apparent pituitary adenomas after 8 and 16 weeks of treatment. The total pituitary cytoplasmic RNA was isolated from treated and control animals and the size distribution pattern of total RNA was obtained by sucrose gradient centrifugation. Estrogen treatment did not change that pattern in the first 4 weeks of treatment, but considerable RNA size distribution changes mainly in the medium size molecular range occurred after 8 and 16 weeks of estrogen administration. It can be hypothesized that an effect of estrogens on pituitary lactotroph hypersecretion and proliferation is not identical with events of irreversible adenomatous cell transformation which occurs later on during chronic estrogen administration.